This invention relates to a method and apparatus for measuring bioelectrical potentials at selected points on the body surface of ovulating women during their menstrual cycles to determine a midcycle peak potential as an indicator of the time of ovulation and thereby provide means for predicting the time for coitus for conception or for predicting the time for abstaining from coitus as an elective means of avoiding conception.
Over the past 20-30 years world attention has been drawn to the types of contraceptive devices and methods of contraception available to women and men. Some devices and methods are more effective than others but may have undesirable effects that make them more or less acceptable and to many individuals not acceptable at all. It is now clear that there is no single contraceptive device or method suitable to a majority of the couples engaging in coitus or contemplating such act. Many physicians have recommended, and many couples have found, that a natural method of family planning is an appealing choice. The appeal may stem from dissatisfaction with known contraceptive devices and means, personal reasons and beliefs (including religious condemnation) or from an interest in gaining better insight into one's own reproductive capabilities or cycles.
Today, natural family planning no longer depends on the "rhythm system," a much criticized and obsolete method of avoiding conception based upon the pattern of menstrual cycle regularity. Rather, the organized collection and graphing of data, such as a woman's basal body temperature, during the reproductive cycle is now used to indicate the fertile/infertile phases of the menstrual cycle. However, the basal body temperature (BBT) graph is monophasic in up to 20% of all ovulating women. Furthermore, a BBT graph is not useful in precisely identifying the time of ovulation because the shift in temperature can be out of synchrony with ovulation by as much as 3-6 days. The BBT graph also cannot be used to accurately predict the time for engaging in coitus for conception since it only indicates in retrospect when coitus should have occurred in order for conception to have taken place. Nevertheless, natural family planning utilizing BBT graphic predictions of ovulation has been shown to be 90% effective for couples spacing their children and 95% effective for those who have attained their desired family size (the difference is due to motivation). This is the same order of effectiveness as barrier contraception (diaphragm) and is considered acceptable for that method. Rather slow acceptance of natural family planning has resulted primarily because of lack of confidence in the BBT curves. Other methods of contraception (IUD's, oral contraceptives, etc.) are more effective but are intrusive of the body and may result in harmful side effects.
As previously stated, the present invention relates to a method and apparatus for determining the time of ovulation by measuring bioelectrical potentials at selected sites on the body surface of ovulating women during their menstrual cycle. Direct current potentials on the dermal (skin) surfaces of man and other vertebrates have long been described, measured and correlated with a variety of biological functions. Standing D.C. potential patterns over the human body were described by H. S. Burr and F. S. C. Northrup in their paper entitled "The Electrodynamic Theory of Life," Quarterly Review of Biology, 1955 10, 322-333. More recently the D.C. potential fields have been mapped with some precision and the pattern has been found to be roughly parallel to the gross anatomical arrangement of the central nervous system. R. O. Becker concluded that two bioelectric data transmission and control systems coexist in man and most other present-day vertebrates, i.e., one a sophisticated, action potential, digital-type system, and the other, a more basic primitive analog-type system, "The Basic Biological Data Transmission and Control System Influenced by Electrical Forces," Annals New York Academy of Sciences, 1974, 236-241. Becker further observed dermal D.C. voltage sources along the course of the peripheral data channels of the analog-type system and noted that such sources show lower resistance and higher voltage values.
An early study by H. S. Burr and L. K. Musselman on menstruation suggested the possibility of recording electrically, ovulation in the healthy human female, "Bio-electric Phenomena Associated with Menstruation," Yale Journal of Biology and Medicine, 1936, 9, 155-58. In 1937, Burr et al were able to document the bioelectric record of the "instant" of ovulation in a human female, "Bio-electric Correlates of Human Ovulation," Yale Journal of Biology and Medicine, 1937, 10, 154-160 and these investigators suggested that it may be possible to obtain bioelectric records of ovulation from points of contact with the body at other than the symphysis pubis and the vagina. Twenty years later, Parsons et al confirmed that vaginal-cervical electropotentials form characteristic cyclic patterns, with a midcycle peak of potential at the time of ovulation, and that midcycle potential change is not found in post-menopausal, irradiated or surgically castrated women, "Abdomino-Vaginal Electric Potential Differences with Special Reference to the Ovulating Phase of the Menstrual Cycle," American Journal of Obstetrics and Gynecology, 1958, 75, 121. They also showed that measured temperature, pH and psychogenic factors, while allied to potential differences, could not give the repetitive and cyclic electrical changes observed during the menstrual cycle in presumed association with periodic ovulation.